ASHLAND, ORE.
— Nobody's very happy with the federal Endangered Species Act - arguably the most powerful of all environmental protection laws.

Scientists and activists say it fails to protect hundreds of "candidate" species headed for extinction because agencies haven't been able to get to them yet for lack of resources or political support. Property rights advocates say the law unfairly harms farmers, ranchers, and developers who have on their land what some deride as an inconsequential bug or weed.

Western governors of both parties say they should have more influence over how the law is defined and enforced. And congressional critics say endangered species protection is really run by judges who make draconian decisions without considering their economic or social impact. Lawmakers are poised to take action.

Scientists have found that the infamous spotted owl here in the Pacific Northwest, listed for years as "threatened" because its habitat had been reduced by logging and other activities, also is under attack by the larger, more numerous barred owl. So they're considering an experiment to "remove" - i.e., kill - some barred owls so that its smaller, spotted cousin will have enough habitat to recover.

On the other hand, the ivory-billed woodpecker - thought to have gone extinct half a century ago - recently has been spotted in an Arkansas swamp.

The politics of species protection has become more complicated as well - particularly as religious groups get involved.

"You can expect to hear from many people of faith as they witness with passion and resolve about the importance of protecting endangered species," Dorothy Boorse told a recent congressional committee. Dr. Boorse teaches biology at Gordon College in Wenham, Mass., and is an evangelical Christian active with the Noah Alliance, a coalition of religious groups that support species protections.

With help from the Endangered Species Act (ESA), some species have done very well, among them the peregrine falcon, the American alligator, the bald eagle, and the California condor.

But of the more than 1,200 species listed as endangered or threatened since passage of the ESA in 1973, very few have recovered to the point where they no longer need special protections such as limiting activity in a designated habitat. "The vast majority of these species have not improved under implementation of current law," says Rep. Richard Pombo (R) of California., chairman of the House Resources Committee. "In fact, there is little evidence of progress in the law's 30-year history.... It checks species in, but never checks them out."

Environmentalists vigorously disagree. Without ESA protections, such as designation of critical habitat, they say many listed species might have fallen into oblivion. Had it not been for the Cache River Wildlife Refuge in Arkansas, for example, the ivory-billed woodpecker might never have survived. Given increasing development, it can take decades and considerable effort to turn a troubled species around, activists and many scientists say.

"Before you can recover a species, you must keep it from tumbling over the final brink to extinction," says Rodger Schlickeisen, president of Defenders of Wildlife. "That's the act's most important function, at which it has been extremely successful."

Meanwhile, Mr. Pombo and other lawmakers are pushing for more rigorous scientific studies before a plant or animal can be listed and therefore require protections. They also want to provide more financial incentives to property owners - at least three-quarters of all listed species reside on private land - and to involve state and local governments more in decisions to list species.

Property rights advocates agree. "Landowners must be compensated when they take land out of production to benefit a species," says Chuck Cushman of the American Land Rights Association in Battle Ground, Wash.

Given the current makeup of Congress, which matches the disposition of the Bush administration to amend the ESA in favor of property rights, such challenges have a good chance of succeeding. Scientists might agree to minor changes to the act. But they often take a much longer view than politicians.

"Earth is faced with a mounting loss of species that equals or exceeds any mass extinction in the geological record," 10 prominent scientists headed by Harvard's E.O. Wilson recently wrote to US Senators. "Habitat destruction is widely recognized as the primary cause of species loss. In the face of this crisis, we must strengthen the [Endangered Species Act] and broaden its protections, not weaken them."